The brakes you have (Avid Shorty 6, according to Mark Livingood) are good, but cantilever brakes are finnicky to adjust. That's the downside of offering many adjusting possibilities.
Another aspect that could help would be to replace your brake pads by Kool Stop Salmon. Compared to the default Shimano or Avid pads, they offer a bit better braking when it's dry, but much better when it's wet, and rim wear is less with Kool Stop than with Shimano or Avid pads.
Regards,